Self-Supporting Bi–Sb Bimetallic Nanoleaf for Electrochemical Synthesis of Formate by Highly Selective CO2 Reduction

Electrocatalytic reduction of CO2 into valuable fuels and chemical feedstocks in a sustainable and environmentally friendly manner is an ideal way to mitigate climate change and environmental problems. Here, we fabricated a series of self-supporting Bi-Sb bimetallic nanoleaves on carbon paper (CP) by a facile electrodeposition method. The synergistic effect of Bi and Sb components and the change of the electronic structure lead to high formate selectivity and excellent stability in the electrochemical CO2 reduction reaction (CO2RR). Specifically, the Bi-Sb/CP bimetallic electrode achieved a high Faradic efficiency (FEformate, 88.30%) at -0.9 V (vs RHE). The FE of formate remained above 80% in a broad potential range of -0.9 to -1.3 V (vs RHE), while FECO was suppressed below 6%. Density functional theory calculations showed that Bi(012)-Sb reduced the adsorption energy of the *OCHO intermediate and promoted the mass transfer of charges. The optimally adsorbed *OCHO intermediate promoted formate production while inhibiting the CO product pathway, thereby enhancing the selectivity to formate synthesis. Moreover, the CO2RR performance was also investigated in a flow-cell system to evaluate its potential for industrial applications. The bimetallic Bi-Sb catalyst can maintain a steady current density of 160 mA/cm2 at -1.2 V (vs RHE) for 25 h continuous electrolysis. Such excellent stability for formate generation in flow cells has rarely been reported in previous studies. This work offers new insights into the development of bimetallic self-supporting electrodes for CO2 reduction.